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TT1.06 - Sub-Microsecond In-Situ X-Ray Diffraction of Bulk Polycrystalline Metals under Dynamic Compression 
December 1, 2014   11:15am - 11:30am

Time-resolved x-ray diffraction can provide important insights into the evolution of the structure of a material during dynamic loading, such as the elastic strains in individual phases, crystallographic texture, and the development of new (possibly metastable) phases. We performed time-resolved x-ray diffraction on bulk polycrystalline metals and alloys undergoing dynamic compressive loading in a split Hopkinson (Kolsky) bar apparatus at strain rates of approximately 2500 s−1 with exposures as short as 70 ns. The diffraction patterns were recorded in transmission onto the Cornell Keck-PAD, a high-speed analog pixel array detector, using 10 keV x-rays from the Cornell High Energy Synchrotron Source (CHESS). Varying the orientation of the Kolsky bar with respect to the incident x-rays and the position of the detector allowed us vary the orientation of the scattering vector with respect to the loading direction. As an example we discuss texture evolution of magnesium alloy AZ31 under dynamic compression. We observed a decrease in scattering from the (0002) planes and a corresponding increase in scattering from the (10-10) planes with the scattering vector perpendicular to the loading axis, while the opposite behavior was observed with the scattering vector approximately parallel to the loading axis. This is consistent with texture evolution in the form of a reorientation of the magnesium lattice due to activation of {10-11}<10-1-2> compression twins in response to dynamic deformation. Finally, we will discuss prospects for future developments in experiments of this kind, taking advantage of new detectors and x-ray sources.

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